The present invention relates to a lifting apparatus which, by frictional engagement with a vertically extending cable of metal or of fiber (rope) is able to, preferably, raise or lower loads along the cable.
The invention relates more particularly to apparatus which does not include a driving drum. It is applied, more specifically, to apparatus of the type including at least two fixed upper and lower pulleys disposed in a coplanar arrangement to cause the cable to follow an S-shaped path around grooves in the pulleys. The driving force produced by a motor mechanism arranged to control rotation of the pulleys is thus linked exponentially to the total angular extent over which the cable engages the pulleys and to the extent of penetration, or wedging, of the cable into the pulley grooves.
At present, a number of types of apparatus known as winches or hoists and not including an entrainment drum have already been proposed.
One apparatus called a "cable pull", is arranged in a manner such that the cable is driven in both directions by two self-clamping jaw blocks. Movement is communicated by a lever and a system of connecting rods with force multiplication in a manner such that the cable passes through the apparatus without being stored therein but must be introduced via one of its ends.
Another apparatus called a "rope hoist" includes a single pulley with a groove arranged with two pawls, one for driving and one for holding stationary. The pulley is disposed between two beams of a support, or frame, and the rope must be introduced into the apparatus via one of its ends.
Another type of apparatus is composed of three driving pulleys keyed to the same shaft and driven by two cranks acting on a pinion and on a toothed wheel. In addition to the need to introduce the cable via one of its extremities, it is necessary to form a loop around each pulley and to slide the cable over a relatively substantial length while turning the cranks to obtain a minimum tension.